This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in German Patent Application No. 101 35 254.9 filed on Jul. 19, 2001 in the name of Danfoss A/S.
1. Field of the Invention
The invention concerns a scroll compressor with at least one fixed displacement element, at least one movable displacement element, which is guided in relation to the fixed displacement element with an orbiting movement, and a gear arrangement, which ensures a non-rotational movement of the movable displacement element, and comprises an axial bearing, via which the movable displacement element is supported in an axial direction.
2. Background of the Invention
A scroll compressor of this kind is known from U.S. Pat. No. 5,180,295. It has a displacement element, which is fixedly connected with a housing of the compressor. An Oldham-coupling moves the movable displacement element in an orbiting manner around an axis in relation to this fixed displacement element. At the same time, the movable displacement element is supported on the housing in the axial direction via the Oldham-coupling and thus held in its position on the fixed displacement element. To permit the orbiting movement and at the same time prevent a rotation of the movable displacement element, the Oldham-coupling has pins projecting both in a direction towards the displacement element and in a direction towards the housing. These pins cooperate with groove-shaped pin paths, which are formed on both the movable displacement element and on the housing. The Oldham-coupling moves along the pin paths in a combination of two linear movements perpendicular to each other. To reduce the friction between the Oldham-coupling and the displacement element or the housing, respectively, both the displacement element and the housing have two roller-bearings, which cooperate with the Oldham-coupling in the axial direction.
With the embodiment described, having two bearing areas on one side of the Oldham-coupling, tilting movements of the movable displacement element may appear. On the other hand, the embodiments with four bearing areas on one side of the Oldham-coupling are very expensive, not least because in this embodiment each bearing area comprises roller bearings.
U.S. Pat. No. 4,259,043 shows a scroll compressor with two mutually orbiting displacement elements, in which the gear arrangement is formed between the movable displacement element and the housing by means of a ball-bearing ring with a plurality of rotatable balls. The balls of this gear arrangement cooperate on both sides of the ball-bearing ring with recesses in the housing or the movable displacement element, respectively. The movement play of the balls in the respective recesses is so large that the movable displacement element is guided in an orbiting manner in relation to the housing and the fixed displacement element. At the same time, the balls, together with the recesses, prevent a rotation of the movable displacement element in relation to the housing. Further, the balls ensure support on the housing in the axial direction of the orbiting movement.
Also with this scroll compressor, the intermediate coupling can be used to prevent a rotary movement of the movable displacement element and to support the movable displacement element in the axial direction. However, the recesses required for each individual ball are very costly to produce.
The present invention is based on the task of improving the support of the orbiting displacement element with a simple design of the scroll compressor.
This task is solved in that the axial bearing comprises three first bearing areas, which cooperate with the movable displacement element.
This is achieved during operation wherein the movable displacement element is supported on the intermediary coupling on three predetermined areas, and thus in a statically determined way. First, a tilting movement of the displacement element in relation to the intermediary coupling is avoided. Second, the axial forces to be transmitted are distributed in a relatively uniform way on all bearing areas, the term xe2x80x9caxialxe2x80x9d referring to the axis, around which the orbiting movement of the movable displacement element occurs. Further, the position of the displacement element in relation to the intermediary coupling is ensured by only three, bearing areas. Thus, it is possible, in spite of a simple design of the scroll compressor to ensure a stable support of the orbiting displacement element.
It is advantageous that the axial bearing comprises exactly three second bearing areas, which cooperate with a supporting part. Thus, next to the stable support of the movable displacement element on the gear arrangement, also a stable support of the gear arrangement on the supporting part is ensured. The supporting part may be a fixedly mounted element, which is arranged, for example, on the housing or on the fixed displacement element. However, it is also possible for the supporting part to be formed by the housing or the fixed displacement element.
It is favourable that the gear arrangement comprises a supporting element, on which at least one of the first bearing areas is arranged opposite to one of the second bearing areas in the axial direction. Thus, the two bearing areas are arranged directly behind each other in the axial direction. An axial pressure force occurring on the movable displacement element can thus be transferred directly to the second bearing area and the supporting part via the first bearing area and the supporting element, without the presence of an internal lever arm between the two bearing areas. This means a substantial reduction of the stress on the supporting element. Thus, it is possible to make the supporting element with a relatively lower axial thickness. In this way, also the axial length of the scroll compressor can be reduced.
Further, it is favourable that each bearing area has a sliding surface. Thus, the bearing surfaces act as linear slide bearings. This means that the axial force transmission from the movable displacement element to the supporting element and/or from the supporting element to the supporting part can also take place during a movement of the supporting element in relation to the movable displacement element and/or the supporting part. This still permits the bearing areas to be manufactured in a simple way.
Further, it is advantageous that the sliding surface has a hydrodynamic profile. This enables improved formation of a lubricant layer between the bearing area and the movable displacement element or the supporting part, respectively. In this way, the frictional losses during operation can be substantially reduced.
It is also favourable that the sliding surfaces are curved in a movement direction, in which the sliding surfaces move in relation to the movable displacement element or the supporting part against which they abut. Thus, it is possible that, next to the effect of functioning as an axial bearing, the supporting element with the bearing areas also permit a good conversion of the orbiting movement of the movable displacement element into two linear movements, which are approximately perpendicular to each other. In this way, it is also possible to achieve improved lubrication in the bearing areas thereby reducing friction and wear in the axial bearing.
An advantage of the present invention is that at least partially, the bearing areas have a surface where lubrication is enhanced. To produce a surface with enhanced lubrication properties, any suitable and known microstructure can be used. By means of such a surface, the friction between the bearing areas and the movable displacement element or the supporting part, respectively, can be further reduced. Thus, the operating conditions of the scroll compressor can be improved.
Preferably, at least one of the bearing areas is formed on a free end of a bearing pin, which cooperates with the movable displacement element or the supporting part approximately perpendicularly to the axial direction. Thus, it is possible in a simple manner to achieve good cooperation between the supporting element and the movable displacement element or the supporting part also approximately perpendicular to the axial direction. This means that, next to the conversion of the orbiting movement into a linear movement, axial forces can be transmitted via the bearing area through the bearing pin. Thus, such a bearing pin fulfils two functions at the same time, which means that manufacture of the scroll compressor can be further simplified.
It is also advantageous that at least one of the bearing pins cooperates with the movable displacement element and at least one other bearing pin cooperates with the supporting part approximately perpendicularly to the axial direction. In this way, cooperation of the movable displacement element with the supporting part via the supporting element approximately perpendicularly to the axial direction can also be realised with a simple embodiment of the scroll compressor.
It is also favourable that two bearing pins project from both an upper side and a bottom side of the supporting element. By means of these two bearing pins it can be achieved that both the movable displacement element and the supporting part can be guided in a stable linear path in relation to the supporting element. Thus, good supporting conditions of the movable displacement element are also ensured approximately perpendicularly to the axial direction.
It is advantageous that three of the bearing pins each comprise a bearing area, each of these pins being arranged on the supporting element in the axial direction opposite to one of the other bearing areas. Thus, with a simple design of the gear arrangement a high stability can be achieved.
It is also advantageous that the bearing pins are substantially the same size. Thus, with a uniform distribution of the bearing pins on the supporting element a good balance can be achieved, which reduces wear.
In an alternative embodiment, the bearing pins can have different sizes. Thus, the size of each bearing pin can be adapted the load that will be exerted on it during operation. This makes it possible to reduce the weight of the gear arrangement.
Further, it is advantageous that the supporting element has an annular shape. Such a design gives an improved flux of force in the supporting element, as the forces acting upon the bearing pins through the orbiting movement of the displacement element will act approximately tangentially upon the ring.
It is advantageous that the three first bearing areas and/or the three second bearing areas are arranged on the annular supporting element at mutual distances of approximately 120xc2x0. In this way it is possible, to maintain a high stability in the support of the movable displacement element.
Further, it is favourable that the supporting element comprises approximately straight connecting elements. In spite of a reduced material consumption, which causes a reduction of the mass of the supporting element and of the occurring inertia forces, a high stability of the supporting element can be achieved.